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365 lines
13 KiB
365 lines
13 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* Wound/Wait Mutexes: blocking mutual exclusion locks with deadlock avoidance |
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* |
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* Original mutex implementation started by Ingo Molnar: |
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* |
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* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <[email protected]> |
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* |
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* Wait/Die implementation: |
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* Copyright (C) 2013 Canonical Ltd. |
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* Choice of algorithm: |
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* Copyright (C) 2018 WMWare Inc. |
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* |
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* This file contains the main data structure and API definitions. |
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*/ |
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#ifndef __LINUX_WW_MUTEX_H |
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#define __LINUX_WW_MUTEX_H |
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#include <linux/mutex.h> |
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struct ww_class { |
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atomic_long_t stamp; |
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struct lock_class_key acquire_key; |
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struct lock_class_key mutex_key; |
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const char *acquire_name; |
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const char *mutex_name; |
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unsigned int is_wait_die; |
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}; |
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struct ww_acquire_ctx { |
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struct task_struct *task; |
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unsigned long stamp; |
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unsigned int acquired; |
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unsigned short wounded; |
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unsigned short is_wait_die; |
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#ifdef CONFIG_DEBUG_MUTEXES |
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unsigned int done_acquire; |
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struct ww_class *ww_class; |
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struct ww_mutex *contending_lock; |
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#endif |
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#ifdef CONFIG_DEBUG_LOCK_ALLOC |
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struct lockdep_map dep_map; |
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#endif |
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#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH |
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unsigned int deadlock_inject_interval; |
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unsigned int deadlock_inject_countdown; |
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#endif |
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}; |
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#ifdef CONFIG_DEBUG_LOCK_ALLOC |
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# define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) \ |
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, .ww_class = class |
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#else |
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# define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) |
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#endif |
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#define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die) \ |
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{ .stamp = ATOMIC_LONG_INIT(0) \ |
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, .acquire_name = #ww_class "_acquire" \ |
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, .mutex_name = #ww_class "_mutex" \ |
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, .is_wait_die = _is_wait_die } |
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#define __WW_MUTEX_INITIALIZER(lockname, class) \ |
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{ .base = __MUTEX_INITIALIZER(lockname.base) \ |
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__WW_CLASS_MUTEX_INITIALIZER(lockname, class) } |
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#define DEFINE_WD_CLASS(classname) \ |
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struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1) |
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#define DEFINE_WW_CLASS(classname) \ |
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struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0) |
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#define DEFINE_WW_MUTEX(mutexname, ww_class) \ |
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struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class) |
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/** |
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* ww_mutex_init - initialize the w/w mutex |
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* @lock: the mutex to be initialized |
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* @ww_class: the w/w class the mutex should belong to |
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* |
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* Initialize the w/w mutex to unlocked state and associate it with the given |
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* class. |
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* |
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* It is not allowed to initialize an already locked mutex. |
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*/ |
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static inline void ww_mutex_init(struct ww_mutex *lock, |
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struct ww_class *ww_class) |
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{ |
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__mutex_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); |
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lock->ctx = NULL; |
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#ifdef CONFIG_DEBUG_MUTEXES |
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lock->ww_class = ww_class; |
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#endif |
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} |
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/** |
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* ww_acquire_init - initialize a w/w acquire context |
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* @ctx: w/w acquire context to initialize |
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* @ww_class: w/w class of the context |
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* |
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* Initializes an context to acquire multiple mutexes of the given w/w class. |
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* |
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* Context-based w/w mutex acquiring can be done in any order whatsoever within |
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* a given lock class. Deadlocks will be detected and handled with the |
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* wait/die logic. |
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* |
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* Mixing of context-based w/w mutex acquiring and single w/w mutex locking can |
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* result in undetected deadlocks and is so forbidden. Mixing different contexts |
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* for the same w/w class when acquiring mutexes can also result in undetected |
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* deadlocks, and is hence also forbidden. Both types of abuse will be caught by |
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* enabling CONFIG_PROVE_LOCKING. |
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* |
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* Nesting of acquire contexts for _different_ w/w classes is possible, subject |
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* to the usual locking rules between different lock classes. |
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* |
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* An acquire context must be released with ww_acquire_fini by the same task |
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* before the memory is freed. It is recommended to allocate the context itself |
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* on the stack. |
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*/ |
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static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, |
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struct ww_class *ww_class) |
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{ |
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ctx->task = current; |
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ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp); |
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ctx->acquired = 0; |
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ctx->wounded = false; |
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ctx->is_wait_die = ww_class->is_wait_die; |
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#ifdef CONFIG_DEBUG_MUTEXES |
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ctx->ww_class = ww_class; |
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ctx->done_acquire = 0; |
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ctx->contending_lock = NULL; |
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#endif |
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#ifdef CONFIG_DEBUG_LOCK_ALLOC |
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debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); |
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lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, |
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&ww_class->acquire_key, 0); |
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mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); |
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#endif |
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#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH |
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ctx->deadlock_inject_interval = 1; |
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ctx->deadlock_inject_countdown = ctx->stamp & 0xf; |
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#endif |
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} |
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/** |
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* ww_acquire_done - marks the end of the acquire phase |
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* @ctx: the acquire context |
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* |
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* Marks the end of the acquire phase, any further w/w mutex lock calls using |
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* this context are forbidden. |
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* |
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* Calling this function is optional, it is just useful to document w/w mutex |
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* code and clearly designated the acquire phase from actually using the locked |
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* data structures. |
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*/ |
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static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) |
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{ |
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#ifdef CONFIG_DEBUG_MUTEXES |
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lockdep_assert_held(ctx); |
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DEBUG_LOCKS_WARN_ON(ctx->done_acquire); |
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ctx->done_acquire = 1; |
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#endif |
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} |
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/** |
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* ww_acquire_fini - releases a w/w acquire context |
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* @ctx: the acquire context to free |
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* |
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* Releases a w/w acquire context. This must be called _after_ all acquired w/w |
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* mutexes have been released with ww_mutex_unlock. |
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*/ |
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static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) |
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{ |
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#ifdef CONFIG_DEBUG_LOCK_ALLOC |
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mutex_release(&ctx->dep_map, _THIS_IP_); |
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#endif |
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#ifdef CONFIG_DEBUG_MUTEXES |
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DEBUG_LOCKS_WARN_ON(ctx->acquired); |
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if (!IS_ENABLED(CONFIG_PROVE_LOCKING)) |
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/* |
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* lockdep will normally handle this, |
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* but fail without anyway |
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*/ |
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ctx->done_acquire = 1; |
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if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC)) |
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/* ensure ww_acquire_fini will still fail if called twice */ |
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ctx->acquired = ~0U; |
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#endif |
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} |
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/** |
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* ww_mutex_lock - acquire the w/w mutex |
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* @lock: the mutex to be acquired |
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* @ctx: w/w acquire context, or NULL to acquire only a single lock. |
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* |
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* Lock the w/w mutex exclusively for this task. |
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* |
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* Deadlocks within a given w/w class of locks are detected and handled with the |
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* wait/die algorithm. If the lock isn't immediately available this function |
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* will either sleep until it is (wait case). Or it selects the current context |
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* for backing off by returning -EDEADLK (die case). Trying to acquire the |
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* same lock with the same context twice is also detected and signalled by |
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* returning -EALREADY. Returns 0 if the mutex was successfully acquired. |
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* |
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* In the die case the caller must release all currently held w/w mutexes for |
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* the given context and then wait for this contending lock to be available by |
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* calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this |
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* lock and proceed with trying to acquire further w/w mutexes (e.g. when |
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* scanning through lru lists trying to free resources). |
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* |
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* The mutex must later on be released by the same task that |
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* acquired it. The task may not exit without first unlocking the mutex. Also, |
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* kernel memory where the mutex resides must not be freed with the mutex still |
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* locked. The mutex must first be initialized (or statically defined) before it |
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* can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be |
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* of the same w/w lock class as was used to initialize the acquire context. |
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* |
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* A mutex acquired with this function must be released with ww_mutex_unlock. |
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*/ |
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extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); |
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/** |
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* ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible |
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* @lock: the mutex to be acquired |
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* @ctx: w/w acquire context |
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* |
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* Lock the w/w mutex exclusively for this task. |
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* |
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* Deadlocks within a given w/w class of locks are detected and handled with the |
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* wait/die algorithm. If the lock isn't immediately available this function |
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* will either sleep until it is (wait case). Or it selects the current context |
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* for backing off by returning -EDEADLK (die case). Trying to acquire the |
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* same lock with the same context twice is also detected and signalled by |
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* returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a |
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* signal arrives while waiting for the lock then this function returns -EINTR. |
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* |
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* In the die case the caller must release all currently held w/w mutexes for |
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* the given context and then wait for this contending lock to be available by |
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* calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to |
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* not acquire this lock and proceed with trying to acquire further w/w mutexes |
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* (e.g. when scanning through lru lists trying to free resources). |
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* |
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* The mutex must later on be released by the same task that |
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* acquired it. The task may not exit without first unlocking the mutex. Also, |
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* kernel memory where the mutex resides must not be freed with the mutex still |
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* locked. The mutex must first be initialized (or statically defined) before it |
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* can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be |
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* of the same w/w lock class as was used to initialize the acquire context. |
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* |
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* A mutex acquired with this function must be released with ww_mutex_unlock. |
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*/ |
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extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, |
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struct ww_acquire_ctx *ctx); |
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/** |
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* ww_mutex_lock_slow - slowpath acquiring of the w/w mutex |
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* @lock: the mutex to be acquired |
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* @ctx: w/w acquire context |
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* |
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* Acquires a w/w mutex with the given context after a die case. This function |
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* will sleep until the lock becomes available. |
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* |
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* The caller must have released all w/w mutexes already acquired with the |
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* context and then call this function on the contended lock. |
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* |
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* Afterwards the caller may continue to (re)acquire the other w/w mutexes it |
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* needs with ww_mutex_lock. Note that the -EALREADY return code from |
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* ww_mutex_lock can be used to avoid locking this contended mutex twice. |
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* |
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* It is forbidden to call this function with any other w/w mutexes associated |
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* with the context held. It is forbidden to call this on anything else than the |
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* contending mutex. |
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* |
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* Note that the slowpath lock acquiring can also be done by calling |
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* ww_mutex_lock directly. This function here is simply to help w/w mutex |
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* locking code readability by clearly denoting the slowpath. |
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*/ |
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static inline void |
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ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) |
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{ |
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int ret; |
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#ifdef CONFIG_DEBUG_MUTEXES |
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DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); |
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#endif |
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ret = ww_mutex_lock(lock, ctx); |
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(void)ret; |
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} |
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/** |
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* ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible |
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* @lock: the mutex to be acquired |
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* @ctx: w/w acquire context |
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* |
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* Acquires a w/w mutex with the given context after a die case. This function |
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* will sleep until the lock becomes available and returns 0 when the lock has |
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* been acquired. If a signal arrives while waiting for the lock then this |
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* function returns -EINTR. |
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* |
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* The caller must have released all w/w mutexes already acquired with the |
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* context and then call this function on the contended lock. |
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* |
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* Afterwards the caller may continue to (re)acquire the other w/w mutexes it |
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* needs with ww_mutex_lock. Note that the -EALREADY return code from |
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* ww_mutex_lock can be used to avoid locking this contended mutex twice. |
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* |
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* It is forbidden to call this function with any other w/w mutexes associated |
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* with the given context held. It is forbidden to call this on anything else |
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* than the contending mutex. |
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* |
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* Note that the slowpath lock acquiring can also be done by calling |
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* ww_mutex_lock_interruptible directly. This function here is simply to help |
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* w/w mutex locking code readability by clearly denoting the slowpath. |
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*/ |
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static inline int __must_check |
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ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, |
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struct ww_acquire_ctx *ctx) |
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{ |
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#ifdef CONFIG_DEBUG_MUTEXES |
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DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); |
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#endif |
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return ww_mutex_lock_interruptible(lock, ctx); |
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} |
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extern void ww_mutex_unlock(struct ww_mutex *lock); |
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/** |
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* ww_mutex_trylock - tries to acquire the w/w mutex without acquire context |
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* @lock: mutex to lock |
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* |
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* Trylocks a mutex without acquire context, so no deadlock detection is |
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* possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. |
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*/ |
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static inline int __must_check ww_mutex_trylock(struct ww_mutex *lock) |
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{ |
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return mutex_trylock(&lock->base); |
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} |
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/*** |
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* ww_mutex_destroy - mark a w/w mutex unusable |
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* @lock: the mutex to be destroyed |
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* |
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* This function marks the mutex uninitialized, and any subsequent |
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* use of the mutex is forbidden. The mutex must not be locked when |
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* this function is called. |
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*/ |
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static inline void ww_mutex_destroy(struct ww_mutex *lock) |
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{ |
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mutex_destroy(&lock->base); |
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} |
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/** |
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* ww_mutex_is_locked - is the w/w mutex locked |
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* @lock: the mutex to be queried |
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* |
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* Returns 1 if the mutex is locked, 0 if unlocked. |
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*/ |
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static inline bool ww_mutex_is_locked(struct ww_mutex *lock) |
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{ |
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return mutex_is_locked(&lock->base); |
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} |
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#endif
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